$f(x) = 3x^{2}+1$ What is the range of $f(x)$ ?
Consider the range of $3x^{2}$ The range of $x^2$ is $\{\, y \mid y \ge 0 \,\}$ Multiplying by $3$ doesn't change the range. To get $3x^{2}+1$, we add $1$. So the range becomes: $\{\, y \mid y ≥ 1 \,\}$.